This station is underground at Charles Street and Baltimore Street in downtown Baltimore. I recall reading about 25 years ago that this station was built to allow a future north-south subway line to be built under this line, with a station for that line also, making Charles Center Station a two-level transfer station like the WMATA Metro Center Station in downtown Washington, D.C. However, I didn't see any evidence in the station of any knock-out panels or anywhere that the connections to the future lower platform might be. See my article

Baltimore Region Rapid Transit System for maps, routes, train, station and cost information about the 1968-proposed 71-mile system and the 1971-proposed 28-mile system. Those system maps show a two-level transfer station at Charles Center.

Above, looking from the east end of the mezzanine toward the west end of the mezzanine. The escalators go down to the train platform. The top level of the station is fare-free and serves as an underground concourse in this part of downtown Baltimore.

Above, looking from the middle area of the mezzanine toward the west end of the mezzanine. The escalators go down to the train platform. The top level of the station is fare-free and serves as an underground concourse in this part of downtown Baltimore. Notice the atrium in the foreground, it serves all three levels.

Above, looking westward toward the west end of the mezzanine. The escalators go down to the train platform. The fare gates are in the background. The top level of the station is fare-free and serves as an underground concourse in this part of downtown Baltimore, and you can see it wrapping around the edge of the station in the upper left and center part of the photo. Notice the neon artwork.

Above, on the platform, a train just stopped in the station.

Above, on the platform. Looking upward is the atrium, where you can see in upward sequence, the mezzanine, the upper concourse, and the roof of the station.

The Baltimore Metro uses some conventional architecture such as the box platform area structure, but has various interesting architectural features such as this atrium, that provide for a rather interesting viewing experience.